Rotary press or tableting machines typically include one or more dies, a feeder mechanism for feeding powder material into each die, and upper and lower punches which are brought together to press the powder material in each die to form a tablet. In advance of a feeding position at which the feeding mechanism feeds powder material into each die, the lower punch is lowered by a lowering cam from a tablet ejection position (where the lower punch is leveled or slightly projects above the die top and a previously formed tablet, when present, is ejected from the die) to an overfill position. Lowering of the lower punch via the lowering cam creates a cavity inside the die that is subsequently filled with powder material at the feeding position, which powder material is compacted after the die passes the feeding mechanism, i.e., by passing the upper and lower punches through a pressing stage.
An example of such a rotary press machine is a rotary press machine designated as 102i Laboratory Tablet Press manufactured by Fette GmbH.
Another example is disclosed in U.S. Pat. No. 6,761,554 which discloses a rotary press machine including a press turret with upper and lower carousels in which upper and lower punch assemblies are removably supported. The punch assemblies include a die portion having a material chamber in which the material to be compressed is delivered.
In prior art rotary press machines, during every revolution of the press turret (regardless of the operating parameters thereof), at least one compact is produced from each die. This unavoidably leads to a waste of powder material during set-up or start-up of the machine as well as during shut down of the machine, since tablets produced at that time are made at a slower speed, or otherwise in the presence of one or more other non-acceptable operating parameters, and thus are invariably imperfect and must be discarded. This drawback is especially significant when rotary press machines are used for research and development purposes at the stage of a new formulation development because in such situations, there is usually only a limited amount of powder material available. Waste of such powder material is therefore an extremely significant problem.
While research press machines of a linear type exist, such as compaction simulators, such machines produce individual tablets and can operate with small amounts of material at high speed but in comparison with rotary machines they are much less efficient in manufacturing larger batches of tablets needed for extensive tests or clinical studies.